The use of microprocessors within circuit breaker trip units such as described within U.S. Pat. No. 4,672,501 entitled "Circuit Breaker and Protective Relay Unit", requires that the microprocessor becomes fully powered-up before the trip unit is capable of performing overcurrent protection.
U.S. Pat. No. 4,428,022 entitled "Circuit Interrupter with Digital Trip Unit and Automatic Reset" inactivates the microprocessor control lines until the circuit breaker power supply has completely enabled the microprocessor within the circuit interrupter trip unit.
To facilitate rapid operation of the circuit breaker trip unit immediately following a circuit interruption, U.S. Pat. No. 4,710,845 entitled "Digital Static Trip Device for Circuit Breaker", describes storing of the last circuit current samples received prior to interruption. The patent further describes the use of an analog trip unit to provide protection during start up and initialization of the trip unit microprocessor.
U.S. Pat. No. 4,489,394 entitled "Microprocessor Power on Reset System" describes a method whereby the microprocessor initialization signal is deferred after power loss until the microprocessor has become completely enabled.
In most circuit interruption devices containing a microprocessor within the trip unit, additional circuit components are used to insure that the microprocessor becomes fully powered up before initialized to commence circuit protection function to avoid both failure to interrupt upon actual overload as well as to prevent interruption under quiescent circuit conditions, as so-called "nuisance" tripping. In certain applications, protection functions and/or application-related configuration data must be read into the microprocessor during the initialization process for the microprocessor to become fully functional. Also required to effect the circuit protection function is the application of the sampling algorithms used by the microprocessor to make the overcurrent determinations.
One example of a sampling algorithm used within a trip unit microprocessor for overcurrent calculation is found within U.S. Pat. No. 5,159,519 entitled "Digital Circuit Interrupter with Improved Sampling Algorithm".
It would be advantageous to provide for both power-up as well as initialization of a circuit breaker trip unit without compromising the ability of the circuit breaker to interrupt upon actual overcurrent or short circuit and without requiring additional circuit components.
One purpose of the invention is to allow rapid power up initialization of the circuit breaker trip unit microprocessor by virtue of the programs resident in the microprocessor without the requirement of additional circuit components.